radio key fob tester- works with rtl-sdr radio dongle
please follow these 3 simple steps:
install an app;
install a rtl-sdr driver app (free):
https://play.google.com/store/apps/details?id=marto.rtl_tcp_andro
connect your rtl-sdr dongle to the phone and enable OTG-host mode in phone settings menu
Some notes:
rtl-sdr dongle is available at ebay for $8 to $30, please check if it comes with OTG cable.
Cheapest "mini" dongles will not detect 868MHz band. If signal level is false high (urban area and good dongle), use it without antenna.